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AQA Chemistry Unit 2 (resit) CHEM2 10th June

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Hydrogen bonding exists between carboxylic acids, only dipole-dipole exists between aldehydes therefore aldehydes are boiled off at a lower temperature than carboxylic acids.

But aldehydes have an O double bonded to a C, that O surely has two lone pairs it can use to hydrogen bond with?

Reply 141

97Y

Original post by ahsan_ijaz

I don't think that's wrong cuz it didn't say le chateliers - it said state the danger or hazard - one of them is hcl is corrosive which is 1 mark

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Acidifying solution would reduce HCl amount though.. It's produced anyway but not more is produced if you acidify.

Reply 142

WhoDaresWins

Original post by 97Y

Acidifying solution would reduce HCl amount though.. It's produced anyway but not more is produced if you acidify.

Wouldn't acidifying cause the p.o.e to shift to the left to produce more Cl2 which is toxic?

Reply 143

97Y

Original post by WhoDaresWins

Wouldn't acidifying cause the p.o.e to shift to the left to produce more Cl2 which is toxic?

You are correct sir!

Reply 144

Nayzar

Original post by RME11

You wouldn't see the H2 being produced, only a pop when you put a lit splint into the test tube.

I put yellow flame (from burning H2) is that wrong?

Reply 145

Sam Webb

Original post by Seclusion

Bond enthalpies aren't ever negative. :]

I think I'm in the wrong chat actually, I think I sat a different paper XD

Reply 146

username1194172

Original post by Sam Webb

But aldehydes have an O double bonded to a C, that O surely has two lone pairs it can use to hydrogen bond with?

Hydrogen bonding only occurs between HNOF

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Reply 147

ELCRE

I think aqa have really let us down by asking for state symbols, i'm do disappointed in myself and in aqa

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Reply 148

ManOfJustTin

Original post by Nayzar

I put yellow flame (from burning H2) is that wrong?

Pretty sure it has to be white flame.

Reply 149

mgill17

Original post by Sam Webb

Did you have to make it negative because it was exothermic?

If this was the C-C bond enthalpy one it was definitely positive. By definition mean bond enthalpies are endothermic because the first part of the mean bond enthalpy definition is that it's the enthalpy *breaking the bond* and bond breaking is an endothermic process

Reply 150

lahigueraxxx

Original post by 97Y

Equilibrium left, produce toxic Cl2

OMG that's what I put! I honestly didn't think it was right ah :')

Reply 151

ahsan_ijaz

My unofficial answers

State two observations and a equation for reaction of mg and steam

Mg + h20 ====) mgo + H2
Observation 1 - white ppt of mgo forms
Observation 2 - h2 gas forms bubbles

State what happens of addition of a solution with sulphate to bacl2 and hno3

- white ppt of baso4 form
- EQ with state symbols - Ba2+ (aq) + SO42-(aq) ====) BaSO4

Write equation for formation of chcl3 from ch3cl

Ch3CL 2cl2 + ====) ChCL3 + 2HCL

Name for mechanism - free radical subsitution

Can't exactly remember the mechanism

Why cu extraction with fe better with ionic EQ? Environmental reason and economic reason?

- Cu2+(aq) + Fe(s) ====) cu(s) + Fe2+ (aq)

So 2 formed forms acid rain why it's bad
CO2 formed in reduction of ZnO which contributes to global warming not

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Reply 152

Nayzar

Original post by ManOfJustTin

Pretty sure it has to be white flame.

I was relating it to sodiums reaction with cold water bc i know that produces hydrogen which then burns with a yellow flame from the heat

Reply 153

ahsan_ijaz

A lot of letter and their was asking for two products am not sure which order but the 2 correct ones were :

- butanal
-Butanone
-3rd mark for saying butanal had c=o end of chain and Butanone in middle

Next Q - structure of alcohol ( displayed formula)

Basically it was 3ch3 attached to OH a tertiary alcohol

Give one Reagant and condition for how you convert that alcohol into Alkene

Conc h2so4
Condition- reflux

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Reply 154

JoelTheJaffaCake

Original post by r p

Only one equation required state symbols. It was: cu2+ + Fe > Fe2+. + Cu

I agree, this was the only question I remember asking for state symbols!

Reply 155

JustOneLastTime

for the reaction with hcl and hclo formed from chlorine and water did i need to use double arrows to show that the reaction was reversible?

and also in regard to the why one would easily be distilled and the other wouldn't it was an aldehyde and a carboxyllic acid i think i mentioned vanderwaals instead of dipole dipole. so vanderwaals between one and hydrogen bonding between the other ....does anyone think my answer would be accepted

lastly for the last question disadvantages of fermentation i wrote co2 is produced, i forgot that this was in fact carbon neutral will i get 0 marks here?

advantages -- glucose is highly abundant - ethene must be manufactured first
-- cant remember

disadvantages - low yield
---- co2 produced greenhouse gas

Reply 156

JoelTheJaffaCake

Everyone here seems to be saying this was easy... I've done every past paper and there's no doubt in my mind that this was a harder paper. You guys might have done very well (and I think I probably got 90ish too), but that doesn't make it an easy paper. I reckon the boundary for an A will be closer to 80 than 85. It reminds me more of the older papers, like 2010, and the boundaries for an A back then were 70ish (but I wouldn't hold out hope for them being that low...).